[vorbis] Low sample rates / bit rates

[Shawn Riley]

Hey guys. I think Vorbis is pretty cool, but since the current OggEnc only offers 44.1kHz, it
limits what I wanted to use it for. So I've been using Lame to get 16kHz mono Vorbis files. I'm
curious about whether Lame does Vorbis encoding the "right" way for non-44.1k stuff, or whether it
just encodes as it would for 44.1k & changes the sample rate on the output, but I'm not sure if
you guys would know how Lame calls the Vorbis encoder... Anyway, I've been resampling to 16k &
applying a 6.4k lowpass filter using ResampAudio (Thanks heaps, Jelle, for the link!), then using
Lame to compress the output file to about 28kbps average bitrate with Vorbis' Mode A, & I think it
should be possible to compress music to 20kbps, but that can't be done currently without doing
some vicious filtering beforehand, & also using 12/11/8 kHz sampling. I think that if one of Ogg's
aims is to completely replace the Real & MPEG formats, then Ogg might be able to tighten the
screws on them by offering lower sample rates & higher compression options. (Think about the
number of 22kHz/56kbps MP3s floating around.) What sort of changes would need to be made to enable
encoding of all sample rates? And I must also mention that "lame --ogg -v4" outshines "lame -b32"
in this realm, & is comparable to "lame -V8".

Shawn
roleypup at yahoo.com

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